After analyzing water samples from 201 municipal water systems from 43 states, the Environmental Working Group found chemicals considered probable human carcinogens in every single water system they tested. (Photo/Smitha Murthy via Flickr)

It may surprise most Americans to know that at least 100 million U.S. citizens are exposed to toxic carcinogens every day when they drink water from municipal water supplies. The announcement was first made by the Environmental Working Group (EWG), an environmental health research and advocacy organization, in a report released earlier this year. It found that 201 of the largest American municipal water systems across 43 states have known thihalomethane contaminants.

“Utilities do the best job that they can treating a big problem with limited resources, but we must do better,” said Jane Houlihan, the group’s senior vice president for research. “It is not uncommon for people to drink tap water laced with 20 or 30 chemical contaminants. This water may be legal, but it raises serious health concerns.”

The Environmental Protection Agency (EPA) says that water with thihalomethanes over 80 parts per billion is unsafe for human consumption. Of the hundreds of locations tested across the U.S., Davenport, Iowa was the only municipality that stayed below the recommended level.

Where do these contaminants come from? It’s difficult for researchers to trace the exact source in each community, but they likely come from agricultural operations, factories, consumer products, wastewater treatment plants and hydraulic fracturing operations.

“In short, more than 100 million Americans served by these large waterworks were exposed to toxic trash,” EWG reports in their study: “Water Treatment Contaminants: Toxic Trash in Drinking Water.”

It’s turns out that this is only part of the story. Researchers also found 119 regulated chemicals — a total of 260 contaminants — in their more than 22 million tap water quality tests, which are required under the federal Safe Drinking Water Act.

Numerous health studies conducted by researchers in Taiwan, France and Spain over the past five years found that levels of thihalomethanes as low as 35 parts per billion in drinking water were associated with increased risk of bladder cancers, still births, miscarriages, birth defects and other diseases.

Overall cancer rates have dropped significantly across the U.S. since a nationwide peak in 1991, according to American Cancer Society statistics. The 20 percent drop is mostly attributed to improvements in detection and treatment, as well as overall lower rates of smoking.

Numbers may be down significantly, but the American Cancer Society reports that 1,660,290 new cancer cases and 580,350 deaths from cancer are projected to occur in the U.S. in 2013.

What is the solution? EWG researchers recommend lowering the limit of tolerable thihalomethane EPA limits. They are also calling for more research into the 600 chemicals commonly found in U.S. drinking supplies. The environmental and health impacts for most of these chemicals remain unknown or understudied.

“Studies have shown that there are more than 600 unwanted chemicals created by the interaction of water treatment disinfectants and pollutants in source water (Barlow 2004, Richardson 1998, 1999a, 1999b, 2003). Most of these water treatment contaminants have not been studied in depth,” EWG reports.

Consumers can use carbon filtration systems to help filter out some of the chemicals thought to be harmful.

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